More than one dielectric ibetween a parallel plate capacitor

Hey, Im having some troubles with this question, the question asks me to calculate the capacitance of a parallel platecapacitor where the plates are seperated by 3mm, and in between the are three layers of dielectric 1mm thick with different relative permitivities. Do I find the total by adding the three permitivities together :S?

P.S I am also given the area of capacitor and the values of the permitivities

Hey, I have set it up but I am still having no luck, I have read through all my notes aswell but I cant find anything about it. In reply to Hootenanny's post, I think that the charge will be equally distributed along the plates.

Hey, I have set it up but I am still having no luck, I have read through all my notes aswell but I cant find anything about it. In reply to Hootenanny's post, I think that the charge will be equally distributed along the plates.

Ok, I have been reading up a lot, and have encountered the notion of electric flux across the dielectrics, but the thing is I need to know the charge of the capacitor to work with electric flux and I do not have it. I have sketched it up but I am not familiar with this kind of problem.

Ok, instead of the previous idea I decided to use a diffeent method and I think it worked. I'm basing this formula on electric flux, and that electric flux will stay constant throughout the capacitor so that Electric flux= e0*er*E , so for three different relative permitivities I have three different electric field stregths so that,

e0*er1*E1=e0*er2*E2=e0*er3*E3 where er1 er2 and er3 are the three different permitiities

and from this we have a consistent set of equations where we can use the formula

E= V/d to get an equation for the voltage across the capactor:

V=E1*d1+E2*d2+E3*d3= &/e0( d1/er1 + d2/er2 + d3/er3 )

and finally I used the formula C=&A/(d1/er1 + d2/er2 + d3/er3 ) where A is teh surface area of the plates on the capacitor.

so this method can provide the capacitance of a parallel plate capacitor with virtually infinite permitivites, assuming you know what they are and you know A. I thought I should share this method withthe forum for any future questions that relate to this one :D